Light-sensitive acid-resistant composition of matter



Patented Sept. 8, 1925.

UNITED STATES THEODOR FREUNDOBFEB AND ROMAN FREUNDOBFEB, OF MUNICH, GERMANY.

LIGHT-SENSITIVE ACID-RESISTANT COMPOSITION OF MATTER.

No Drawing.

To all whom it may concern:

Be it known that we, THEODOR FREUN- nonrnr. and ROMAN FREUNDORFER, citizens of German residing at Munich, Bavaria,

Germany, ave invented certain new and useful Improvements in Light-Sensitive Acid-Resistant Composition of Matter; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a. light-sensitive acid-resistant composition of matter adapted for application to the metal lates in the process of making etched printing-plates by the photo-mechanical process.

The object of the present invention is attained by making use of the following circumstance: If an ammoniacal solution of shellac is mixed with a bichromate it becomes sensitive and any metal-plates treated with this light-sensitive acid-resistant varnish or coating may be, completely etched after printing and developing, without requiring any further operations. At the same time the film has the pro erty that it will not be dissolved by any of t e customary plate-cleaning agents.

Our varnish'or coating ma be conveniently prepared as follows issolve in a water bath 17 0 grams shellac powder in 700 1 0. cm. distilled water and 200 0. cm. ammonia of 0.910 specific gravity. Frequent agitation Application filed November 22, 1921. Serial No. 618,889.

is desirable, and the powder will be found to be entirely dissolved when the mixture reaches the boiling point. The solution is then cooled and has added thereto 30 0. cm. of a 10% solution of ammonium bichromate.

The varnish is then ready for use and may 40 be preserved for from three to four weeks.

In using our varnish, the zinc plate is carefully cleaned with very fine emery dust and slightly roughened in a. nitr1c acid bath, and the varnish a plied in the same manner as when fish g ue solution is employed. The applied layer should be thick enough so that no rainbow colors ap ear and that the completed print shows a sight relief. Care should be taken to distribute the 60 varnish absolutely uniformly as inequalities are readily noticeable in the final product. The time of ex osure is approximately the same as for fis lue. The plates are developed in a bat of 1000 0. cm. 96% alcohol and 2 methylviolet B B extra concentration. fivelopment is completed in two to three minutes.

Accordin ly what is claimed as new and sou ht to be protected by Letters Patent is t e following:

A composition of matter for a li ht-sensitive film comprisin an ammoniaca .shellac solution and a solub e bichromate.

In testimony whereof we hereunto aflix our signatures.

THEODOR FREUNDORFER. ROMAN FREUNDORFER. 

